Space Solar Panels of Increased Reliability . / February 8, 2017 /

The „Russian Space Systems“ Holding Company (RKS, part of the ROSCOSMOS State Corporation) has completed the construction of the modernized system of electrical protection for the domestic production solar panels. The system will extend significantly the spacecraft power source life and make the Russian solar panels be the most power efficient ones in the world.

The solar panel protection system is based on diodes  small devices installed on each photoelectric transducer constituting a solar panel. Diodes are one of the key elements which quality governs the power efficiency and active lifetime.

Photoelectric transducers are arranged in the form chains called „string“. Once solar panel is shaded completely or partially, photoelectric transducers begin to consume current instead of feeding it to storage batteries. To avoid this, each photoelectric transducer has a shunt diode and each string – a blocking diode. Diodes work in a similar way when with time some photoelectric transducers or string fail to operate affected by the outer space destabilizing factors – such elements are simply removed.

Alexey Anurov, RKS says: „Nearly twenty years ago, RKS was the first to begin producing fuse diodes and is making now their updating in Russia. In last year, we completed the development of a new generation of these products. The products are not inferior to the best world analogues by their electrical, mass and reliability characteristics and lead them by some parameters. The Russian diodes are at half the price of their foreign analogues.“

The new diode construction uses the patented technical solutions to improve substantially their performance characteristics and increase the reliability. For example, the specially designed multilayer dielectric isolation of crystal allows a diode to withstand up to 1.1kVe reverse voltage. A new generation of fuse diodes may thus be used along with the most efficient existing photoelectric transducers.

To increase the reliability and lifetime of diodes, RKS developed the new multilayer molybdenum-based diode commutating buses that enable the diodes to withstand more than 700 thermal shocks when the temperature varies by more than 300 degrees Celsius for several minutes. A special protective coating of all diode metallic components preventing from surface oxidation when in contact with corrosive media is one more innovation. This also extended the device storage life from one to five years.

Pavel Didyk, Senior Fellow, RKS says: „Owing to innovative design solutions the active lifetime of spacecraft solar panel equipped with new diodes has increased to 15.5 years. The diode may be stored on Earth for another five years. Thus, the total warranty operation life of new generation of diodes is 20.5 years. A high reliability of the device was confirmed by independent resource tests during which the diodes withstood more than seven thousand thermal shocks.“

In the USSR, solar panels used only the blocking diodes thus resulting in a rapid degradation in solar panels. In the1990s, the foreign production photoelectric transducers were widely used in manufacturing the home spacecraft.Andrey Basovsky, Head of fuse diode development team says: „For the first time, the Russian shunt diodes have been produced as the joint effort of specialist from RKS and „NPP „KVANT“ JSC in constructing solar panels for the International Space Station. Since that time, RKS remains the key supplier of diodes for home production solar panels. The operating experience has demonstrated that our electrical protection system decreases the solar panel degradation by about 10 times.“

Photoelectric transducer is 25 × 50mm in size and solar panels may be 100 square meters in area, and therefore the solar panel manufactures require tens of thousands diodes per year. The proven batch technique allows for RKS to produce more than 15 thousand diodes of new generation per year. The diode delivery is scheduled to start in 2017.